Ethan seems like a normal ten-year-old, but he has a secret. It's not that he's the one who accidentally filled the sunblock container with glue last summer or that he cracked the screen on his sister's phone and blamed it on their baby brother. (Those things may have happened, but they've got nothing on this.) No, Ethan's secret is that he knows time travel is real--because his future self keeps coming back to visit him.

Lucky Ethan, right?

Wrong. Because when Ethan's future self shows up, he tends to bring bad news, and he's kind of bossy. (Not to mention he's always wearing super weird clothes.) This time around, he's asking Ethan to do one simple thing: make sure today's substitute teacher doesn't quit, or else one day she'll become an evil dictator who will destroy the planet. But his future self clearly forgot what fourth grade is like, because if there's one thing Ethan's class is great at (other than losing their homework), it's tormenting substitute teachers...